1. Field of the Invention
The present disclosuer relates to an electrophoretic display device and its fabrication method and, more particularly, to an electrophoretic display device capable of minimizing a step at a protection layer and minimizing the number of masks used in a fabrication process.
2. Discussion of the Related Art
In general, an electrophoretic display device is an image displayer using a phenomenon that when a pair of electrodes receiving voltage are put in a colloid solution, colloid particles are moved to one polarity.
The electrophoretic display device is a display device in which a transparent conductive film is coated on a base film which is thin and can be easily bent like paper or plastic to drive electrophoretic suspension and receives much attention as electric paper that may replace the conventional printing mediums such as books, newspapers, and the like.
The general electrophoretic display device will now be described with reference to the accompanying drawings.
As shown in FIG. 1, an electrophoretic panel provided in the general electrophoretic display device includes a first substrate 1 on which gate lines 4 and data lines (not shown) are formed to cross each other to define a plurality of pixels, and a second substrate 2 disposed to face the first substrate 1.
With reference to FIG. 1, the plurality of pixels defined on the first substrate 1 include a plurality of vertical pixel rows and a plurality of horizontal pixel rows. Data lines are formed on every vertical pixel row on the first substrate 1. A thin film transistor (TFT) 5 including a source electrode 5a, a drain electrode 5b, an organic semiconductor layer 5c, a gate insulating layer 5d, and a gate electrode 5e is formed at each pixel, and a pixel electrode 9 in contact with the drain electrode 5b of the TFT 5 is formed at each pixel.
A passivation layer 8 is formed on the data lines, the TFT 5, and the pixel electrode 9 formed on the first substrate 1. Recently, in order to prevent a pixel voltage applied to the pixel electrode 9 to drive an electrophoretic film from weakening due to the thick passivation layer 5, an open area (OA) is formed at the passivation layer 8 by removing a portion or the entirety of a region overlapping with the pixel electrode 9.
The gate line 4 is formed at every horizontal pixel row on the passivation layer 8 of the first substrate 1 and is in contact with the gate electrode 5e of the TFT 5 via a contact hole 6 provided at the passivation layer 9.
With reference to FIG. 1, a common electrode 10 is formed on the second substrate 101, and the electrophoretic film (not shown) is formed between the first and second substrates 1 and 2.
Although not shown, the electrophoretic film includes a plurality of capsules in which electronic ink including white ink and black ink is distributed, and the white ink and the black ink are charged with each different polarity. Namely, white ink is charged with positive electric charges, and black ink is charged with negative electric charges, or vice versa.
A method for fabricating the general electrophoretic display device having such configuration will be described as follows.
First, a first masking process is performed to form the source electrode 5a, the drain electrode 5b and a data line (not shown) on the first substrate 1 with a plurality of pixels defined thereon.
Next, a second masking process is performed to form the pixel electrode 9 in contact with the drain electrode 5b at each pixel of the first substrate 1.
And then, a third masking process is performed to form the organic semiconductor layer 5c, the gate insulating layer 5d, and the gate electrode 5e at each pixel of the first substrate 1.
Thereafter, the passivation layer 8 is formed on the data line, the TFT 5, and the pixel electrode 9 of the first substrate 1.
Subsequently, a fourth masking process is performed to form the contact hole 6 exposing a portion of the gate electrode 5e at the passivation layer 8, and the open area (OA) is formed to expose a portion or the entirety of the pixel electrode 9.
And then, a fifth masking process is performed to form the gate line 4 on the passivation layer 8. At this time, the gate line 4 is in contact with the gate electrode 5e via the contact hole 6 of the passivation film 8.
In the fabrication method, the first to third masking process includes a step of sequentially forming an element formation material layer (e.g., a pixel electrode formation material layer) and a photosensitive film; a step of forming a photosensitive film pattern by performing photolithography on the photosensitive film; and a step of patterning the element formation material layer by using the photosensitive film pattern.
The related art general electrophoretic display device as described above requires 5 masks in its fabrication process, which, thus, is ineffective in the fabrication costs and time. Thus, an electrophoretic display device having a structure of requiring the minimum number of masks in the fabrication process and its fabrication method are required.
The first substrate 1 and the plurality of elements on the first substrate 1 of the general electrophoretic display device as described above may be applicable to a TFT array substrate of a liquid crystal display (LCD) device. However, when the first substrate 1 and the plurality of elements on the first substrate 1 of the general electrophoretic display device are applied to the TFT array substrate of the LCD device, rubbing of an alignment film is not smoothly made due to a step at the open area (OA) formed at the passivation layer 8 or a region may not be filled with liquid crystal, degrading picture quality.